JPS5828708B2 - mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mass spectrometer equipped with an electromagnetic device that generates a magnetic field for analysis, and particularly to a mass spectrometer that can eliminate the adverse effects caused by fluctuations in the magnetic field for analysis caused by lines of external magnetic force coming from the outside. It is related to the device.

The analysis magnetic field of a mass spectrometer is required to have smaller fluctuations in strength as the resolution of the device becomes higher.

Conventionally, therefore, a magnetic field strength detection element such as a ball element is placed in the magnetic field, the detection signal from the element is compared with a reference signal, and the excitation current is controlled so that the difference becomes zero, so that the magnetic field strength is always constant. I'm trying to make it happen.

With such conventional methods, relatively large and slow magnetic field fluctuations can be canceled out.

However, it is necessary to increase the loop gain of the control system in order to cancel out minute fluctuations in the analysis magnetic field caused by external magnetic lines of force that enter the yoke of the electromagnet, excitation coil, etc. that generate the analysis magnetic field from outside the analysis magnetic field, such as a power transformer. , there is a limit because it may cause oscillation of the system.

The present invention has been made in view of this point, and detects by disposing a detection coil in the magnetic circuit of an electromagnet that generates a magnetic field for analysis, and a correction magnetic field generating means on the ion path outside the magnetic circuit. It is an object of the present invention to provide a mass spectrometer that can eliminate the adverse effects of ions caused by fluctuations in an analytical magnetic field by integrating the output signal of the coil and supplying the integrated signal to a correction magnetic field generating means.

The present invention will be explained in detail below using the drawings.

The drawing is a configuration diagram showing an embodiment of the present invention.

In the figure, 1 and 2 are magnetic poles for generating a magnetic field for analysis, 3 and 4 are pole pieces, 5 and 6 are excitation coils, and 1 is a magnetic field control power source.

Ions (2) from an ion source (not shown) enter the analysis magnetic field formed between the pole pieces 3 and 4, are deflected according to the mass-to-charge ratio, and are emitted outside the magnetic field.

A magnetic field strength detecting element 8 such as a Hall element is disposed within the magnetic field, and a detection signal obtained from the element 8 is sent to the magnetic field control power source I via an amplifier 9.

Since the control power source 1 controls the excitation current supplied to the coils 5 and 6 based on the difference signal between the detection signal and the reference signal, the analytical magnetic field formed between the pole pieces is maintained at a constant strength. Become.

As mentioned above, such a control system cannot cancel minute fluctuations in the analytical magnetic field caused by external lines of magnetic force.

Therefore, in the present invention, the following configuration is added.

That is, 10 is a detection coil arranged in the magnetic circuit of the electromagnet that generates the analytical magnetic field, and for detecting fluctuations in the analytical magnetic field;
Reference numeral 11 denotes an auxiliary coil disposed on the ion path behind the analysis magnetic field and for generating a correction magnetic field in the same or opposite direction as the analysis magnetic field.

The detection signal obtained from the detection coil 10 is transmitted to an amplifier 12.
The signal is sent to the integrating circuit 13 via.

The output of the integrating circuit 13 is then passed through a phase shift circuit 14 to a drive circuit 15 for supplying current to the auxiliary coil 11.
sent to.

In such a configuration, the detection signal dφ obtained from the detection coil 10 is t corresponding to the rate of change of the analysis magnetic field φ, and the output of the integrating circuit 13 that integrates this signal is a signal corresponding to the change in the magnetic field φ. is obtained.

Strictly speaking, this signal has a phase shift with respect to the change in the magnetic field φ due to the 7-integrator circuit 13, amplifier 12, etc., so the signal is adjusted so that the phase shift is zero by the phase circuit 14, and then the drive circuit 15 to the auxiliary coil 11.

Based on the signal, the auxiliary coil 11 generates a magnetic field in the direction (opposite phase) that cancels out the erroneous deflection received by the ions due to fluctuations in the analysis magnetic field. The resulting deflection is canceled out.

If the winding direction of the coil 11 is reversed, the signal may be inverted by the drive circuit 15 or the amplifier 12, or the phase shift amount of the phase shift circuit may be further shifted by 1800.

In the above embodiment, the auxiliary coil 11 is placed behind the analysis magnetic field, but it may be placed in front, and the detection coil 10 may be placed anywhere in the magnetic circuit of the electromagnet.

As described in detail above, according to the present invention, fluctuations in the magnetic field for analysis are canceled by the separately provided auxiliary coil, so minute fluctuations can be canceled with a fast response speed.

[Brief explanation of the drawing]

The drawing is a configuration diagram showing an embodiment of the present invention. 1.2: magnetic pole, 3, 4: ball piece, 5, 6: excitation coil, 10: detection coil, 11: auxiliary coil, 13: integrating circuit, 14: phase shifting circuit.

Claims (1)

[Claims] 1. A mass spectrometer comprising an electromagnetic device that generates an analytical magnetic field for separating ions according to their mass-to-charge ratio; a detection coil disposed in a magnetic circuit of the electromagnetic device; and a magnetic circuit of the electromagnetic device. A mass spectrometer comprising: a correction magnetic field generating means disposed in an outer ion path; and an integrating circuit for integrating a detection signal from the detection coil and supplying the integrated detection signal to the correction magnetic field generating means.